The Taoiseach says he will raise the Emma De Souza case with British Prime Minister Boris Johnson this week.
Its after the British Home Office won an appeal against an immigration case taken by the Derry woman.
It effectively means people in Northern Ireland remain British under UK law, even if they identify as Irish.
The Dáil has heard claims the ruling is in breach of the Good Friday Agreement.
Taoiseach Leo Varadkar says it's something he will discuss with Boris Johnson:
File image: Leo Varadkar/RollingNews